A submount described in Japanese Laid-Open Patent Publication No. 2005-093804, for example, is known as a submount for mounting a semiconductor laser element. In the submount disclosed in the abovementioned Japanese Laid-Open patent publication, a metal electrode is formed on the surface thereof, and a marker for positioning a semiconductor laser element is formed on a part of this. The shape of the marker is one that will be recognized by the edge of the metal electrode.